The effect of competition and horizontal trait inheritance on invasion, fixation, and polymorphism

JOURNAL OF THEORETICAL BIOLOGY

卷:411

Article

Billiard, Sylvain¹  Collet, Pierre²  Ferriere, Regis^3,4  Meleard, Sylvie⁵  Viet Chi Tran⁶ 

[1] Univ Lille, CNRS, UMR Evoecopaleo 8198, F-59000 Lille, France

[2] Univ Paris Saclay, CNRS, Ecole Polytech, CPHT, Route Saclay, F-91128 Palaiseau, France

[3] PSL Res Univ, Ecole Normale Super, Ecoevolut Math, CNRS UMR 7625, 46 Rue Ulm, F-75230 Paris 05, France

[4] Univ Arizona, Dept Ecol & Evolutionary Biol, Tucson, AZ 85721 USA

[5] Univ Paris Saclay, CNRS, Ecole Polytech, CMAP, Route Saclay, F-91128 Palaiseau, France

[6] Univ Lille, CNRS, UMR Lab P Painleve 8524, UFR Math, F-59000 Lille, France

关键词: Horizontal gene transfer;    Stochastic individual-based models and their limits;    Mobile genetic elements;    Plasmid;    Bacterial conjugation;    Fixation probability;    Invasion;   

DOI  :  10.1016/j.jtbi.2016.10.003

来源: Elsevier

【 摘 要 】

Horizontal transfer (HT) of heritable information or 'traits' (carried by genetic elements, plasmids, endosymbionts, or culture) is widespread among living organisms. Yet current ecological and evolutionary theory addressing HT is scant. We present a modeling framework for the dynamics of two populations that compete for resources and horizontally exchange (transfer) an otherwise vertically inherited trait. Competition influences individual demographics, thereby affecting population size, which feeds back on the dynamics of transfer. This feedback is captured in a stochastic individual-based model, from which we derive a general model for the contact rate, with frequency-dependent (FD) and density-dependent (DD) rates as special cases. Taking a large population limit on the stochastic individual-level model yields a deterministic Lotka-Volterra competition system with additional terms accounting for HT. The stability analysis of this system shows that HT can revert the direction of selection: HT can drive invasion of a deleterious trait, or prevent invasion of an advantageous trait. Due to HT, invasion does not necessarily imply fixation. Two trait values may coexist in a stable polymorphism even if their invasion fitnesses have opposite signs, or both are negative. Addressing the question of how the stochasticity of individual processes influences population fluctuations, we identify conditions on competition and mode of transfer (FD versus DD) under which the stochasticity of transfer events overwhelms demographic stochasticity. Assuming that one trait is initially rare, we derive invasion and fixation probabilities and time. In the case of costly plasmids, which are transfered unilaterally, invasion is always possible if the transfer rate is large enough; under DD and for intermediate values of the transfer rate, maintenance of the plasmid in a polymorphic population is possible. In conclusion, HT interacts with ecology (competition) in nontrivial ways. Our model provides a basis to model the influence of HT on evolutionary adaptation.

【 授权许可】

Free